Catheter with retractable cover and pressurized fluid

ABSTRACT

Apparatus and method for delivering and deploying an intravascular device into the vessel including an outer and inner tube that are axially linked by a housing structure at the proximal end of the catheter, and a retractable sleeve structure having a middle tube and sleeve tip. The sleeve tip is sealed to the inner tube at the distal end, and continuously extends into the middle tube. At the proximal end of the sleeve structure, the middle tube is sealed to either a housing structure or slideable proximal ring, forming a sealed chamber between the inner tube and the sleeve structure. A radial space is formed between the sleeve tip and the inner tube optimized for intravascular device placement. During retraction of the sleeve structure, the fold of the sleeve tip peels away from the device, which expands to its deployed state while minimizing axial forces and friction.

This application is a continuation of U.S. application Ser. No.14/775,569, filed Sep. 11, 2015, which is a National Stage Entry ofPCT/IB2013/002770, filed Jul. 23, 2013, which is a continuation-in-partof U.S. Ser. No. 13/560,132, filed Jul. 27, 2012, issued as U.S. Pat.No. 9,364,358 on Jun. 14, 2016; all of which are incorporated byreference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates to the field of catheters, in particular acatheter system with a retractable sleeve structure for use, forexample, in delivery and deployment of an intravascular device. Thecatheter system is specifically designed for use in the delivery of anintravascular device through tortuous vessels and its deploymenttherein.

BACKGROUND

Transluminally implantable intravascular devices, such as stents orgrafts, are initially mounted upon or within a delivery catheter andthen crimped into a compact configuration of a relatively small diameterto facilitate insertion and transluminal advancement of the device intothe desired lesion requiring treatment. Thereafter, such devices areradially expanded to a larger operative diameter either by removing aconstraining layer thereby releasing the device or by inflating aballoon on which the device is crimped. When expanded the device servesto support the vessel against its tendency to reclose and may also serveas a matrix for releasing a medically active substance.

It will be appreciated that the term “stent” may be used herein below asa general and non-limiting example of a catheter-mounted intravasculardevice. Both self-expanding and balloon expandable stents are well knownand widely available in a variety of designs and configurations.

Prior art catheter systems for stent delivery provided a restrainingsheath overlying the stent. One problem that arises when mounting thestent on the catheter system as well as during retraction of the sheathis excessive friction and rubbing between the sheath and the stent thatmay complicate and sometimes render stent deployment impossible. Inaddition, stents are often coated with a special polymer, a drug, or acombination thereof. Excessive friction and rubbing between the stentand the constraining sheath may cause damage to the integrity of thecoated surface material of the stent by the friction between the sheathand the external surface of the stent. Moreover, such friction tends toincrease even more when using longer stents or stents with a narrowercrimping profile. Accordingly, it is an object of the invention tominimize friction between the catheter and the stent during deployment.

Another problem in the art arises with stents having relatively lowaxial rigidity, where axial friction forces applied during deployment ormounting of the stent on the catheter system may shorten the stent. Itis therefore advantageous to have a catheter system that minimizes axialfriction forces applied to the stent during deployment and mounting.

Yet another problem known in the art is related to the size of theproximal portion or the handle of catheter systems of self-expandablestents. Deploying such stents requires pulling the constraining sheathbackward in the proximal direction a length which equals at least thelength of the stent. When using longer stents (i.e. 100 millimeters andmore) this limitation becomes a disadvantage as it leads to relativelylong handles with a bulky mechanical structure that may be uncomfortableto operate. It is therefore advantageous to have a catheter system witha relatively short handle.

SUMMARY OF THE INVENTION

The present invention relates to a catheter system with a retractablesleeve structure and a method of using the catheter system. The cathetersystem comprises a multi-component tubular structure capable ofdeploying an intravascular device while minimizing axial frictionalloads on the device during deployment. The catheter system of theinvention uses a retractable sleeve structure filled with fluid duringdelivery and deployment. The catheter system comprises an inner tubedisposed coaxially with an outer tube, wherein the inner tube comprisesan interior lumen for a guide wire and an exterior surface on which aretractable sleeve structure is mounted. The outer tube forms a lumenfor each of the guide wire, inner tube and the retractable sleevestructure.

The retractable sleeve structure extends through the length of the innertube and forms a sealed chamber therewith. The retractable sleevestructure comprises a middle tube and a distal sleeve tip, the sleevetip forming a fold over the distal end of the intravascular devicethereby creating a double layered sheath around the device. The doublelayered sheath, when pressurized with fluid, may be pulled back, therebyreleasing the device without exerting any friction forces thereon.

The invention also relates to a method of deploying an intravasculardevice. The method comprises the steps of filling the sealed chamberwith fluid, navigating the catheter to a target site, positioning thesleeve tip with a mounted device at the target site, pressurizing thefluid and pulling the retractable sleeve structure proximally, therebycausing the sleeve tip to unfold and release the device at the targetsite exerting minimal friction forces on the device. In one embodimentthe retractable sleeve structure is pulled back by sliding a handleconnected to a proximal portion of the middle tube. In anotherembodiment the retractable sleeve structure is pulled back by applying aforce to a collapsible proximal portion of the middle tube using, forexample, a knob or wheel. The force in the proximal direction may pushthe collapsible proximal portion towards the proximal end of the housingstructure, thereby collapsing the collapsible portion, for example, inan accordion-like fashion. This embodiment has an advantage that itenables the use of a shorter guide wire and shorter housing compared toother catheter systems, and is particularly useful when using relativelylong stents. In another embodiment, the retractable sleeve structureincludes a rear retractable portion that is affixed to an insertion tubeand folds back onto itself, thus retracting the sleeve tip and deployingthe stent. In yet another embodiment, the inner tube includes a curvedportion at the proximal end that coils within the housing structure;thus, the retractable sleeve structure is retracted over the curvedportion during deployment. These embodiments likewise have an advantagethat they enable the use of a shorter housing compared to other cathetersystems, and further enable easier operation of the retractable sleevestructure.

Another aspect of the invention relates to a method of mounting anintravascular device onto the catheter system. In one embodiment themethod comprises the steps of retracting the sleeve tip to an unfoldedposition, filling the retractable sleeve structure with fluid, andholding a crimped intravascular device onto the inner tube with aseparate device, and advancing the sleeve tip over the crimpedintravascular device thereby forming a fold over a portion of thecrimped intravascular device. In this mounting embodiment, theintravascular device is released, the catheter system is pulledproximally, and the process is incrementally repeated until theintravascular device is mostly or entirely located under the fold of thesleeve tip. Once the intravascular device is fully sheathed by the fold,the method may further comprise releasing fluid into the sealed chamberfor storage. This aspect of the invention may be useful in particular tomount an intravascular device onto a catheter system for laterdeployment according to the method of deploying an intravascular deviceindicated above.

Storage of the catheter system may be accomplished at a neutral airpressure. However, prior to use, the air in the retractable sleevestructure is replaced with fluid through the use of a sealable port.During this process, any residual air in the sleeve structure may beevacuated through a micro-orifice in the fold of the sleeve tip.

DESCRIPTION OF DRAWINGS

FIG. 1A illustrates a cross-section of the catheter system in apre-deployment state according to the principles of the invention.

FIG. 1B illustrates an enlarged portion of FIG. 1A.

FIG. 2 illustrates a cross-section of the catheter system in a stage ofpartial deployment of an intravascular device as the sleeve tip of theretractable sleeve structure is partially withdrawn by sliding thehandle one-third of the distance toward the proximal end of the housingstructure.

FIG. 3 illustrates a cross-section of the catheter system in a stage ofpartial deployment of an intravascular device as the sleeve tip of theretractable sleeve structure is partially withdrawn by sliding thehandle two thirds of the distance toward the proximal end of the housingstructure.

FIG. 4 illustrates a cross-section of the catheter system in apost-deployment state according to the principles of the invention.

FIG. 5A-5B illustrate a cross-section of one alternative embodiment ofthe catheter system according to the principles of the present inventionin pre-deployment and post-deployment stages.

FIGS. 6A-6C illustrate a cross-section of another alternative embodimentof the catheter system according to the principles of the presentinvention in pre-deployment and post-deployment stages.

FIGS. 7A-7B illustrate a cross-section of another alternative embodimentof the catheter system according to the principles of the presentinvention in pre-deployment and post-deployment stages.

FIGS. 8A-8D illustrate a half of a cross-section view of a method ofplacing the intravascular device onto the catheter system and under theconstraining sheath.

The intravascular devices shown in these Figures are two-dimensionalrepresentations of the intravascular device embodiments of the instantinvention. The skilled artisan will recognize that the device is athree-dimensional structure having a cylindrical portion, as describedfurther below.

DETAILED DESCRIPTION OF THE INVENTION

The catheter system with a retractable sleeve structure of the inventionallows an intravascular device to be delivered to a target vesselwithout subjecting the device to frictional forces during deploymentassociated with other delivery systems using a constraining sheath. Thecatheter system of the invention includes an elongate inner tubedefining proximal and distal ends and a lumen extending longitudinallytherethrough wherein a guide wire is movably disposed. The cathetersystem further includes an elongate outer tube having a proximal and adistal end, wherein the inner tube coaxially extends therethrough alongthe entire length. The inner tube and outer tube are affixed to ahousing structure in the proximal portion of the catheter system, thehousing structure includes a distal opening to which the outer tube isaffixed, as well as a proximal opening to which the inner tube isaffixed. “Distal” is defined herein as being closer to the insertion endof the catheter (i.e. the end typically inserted into the body) and theterm “proximal” is defined as being closer to the end of the catheterthat generally remains outside the body, as demarcated by line X in theFigures herein.

A retractable sleeve structure having a proximal and a distal endextends through the axial space created between the inner and the outertubes. The retractable sleeve structure comprises a middle tube and asleeve tip which coaxially extends substantially along the length of theinner and outer tubes. The retractable sleeve structure may be sealinglyconnected to the inner tube at the distal end with a distal ring therebyforming a sealed chamber. In a pre-deployment state the intravasculardevice is mounted in a radial space created between the inner tube and adouble layered sheath created by folding the sleeve tip onto itself.

The outer tube, the middle tube and inner tube may be manufactured fromkink resistant and flexible materials or composite structures, forexample polyether ether ketone (PEEK), polyethylene terephthalate (PET),Polyimide (PI), braided Nylon 12 or suitable materials readilyunderstood in the art. The method of affixing the outer tube and innertube to the housing structure can be achieved through methods that arewell known in the art. Non-limiting examples of joining methods includefusing (e.g. heat fusion), welding (e.g. ultrasonic welding) and joiningby adhesive methods (e.g., gluing). Combinations of these methods andmaterials are contemplated by this invention.

The sleeve tip is manufactured from materials having sufficient radialrigidity to prevent expansion beyond a desired maximum diameter.Non-limiting examples include ultrathin polyethylene terephthalate (PET)or a Polyimide (PI). Advantages of a sleeve tip formed by PET includeflexibility. In one embodiment, the sleeve tip is formed of a materialabout 5-20 micrometers thick, preferably 10 micrometers thick. The twoadjacent portions of the sleeve tip created by the fold, i.e. the innerand outer portions of the fold, are maintained apart from each otherpreferably by a few micrometers so as to avoid rubbing against eachother; such separation is enabled by pressurizing sealed chamber.Alternatively, or in addition, the interior surface of the sleeve tipmaterial may be coated with a dry hydrogel which when wetted—e.g. by thefilling of the retractable sleeve with fluid—will swell and form asufficiently rigid sleeve tip, minimizing or cancelling the need forpressurization. Hydrogels useful in this embodiment include for example,polyvinylpyrrolidone (PVP) or TG-2000 (Life Science Polymers), but otherhydrogels known in the art will be equally useful. The method ofcombining or joining the sleeve tip and other components of theretractable sleeve structure can be achieved through methods that arewell known in the art. Non-limiting examples of joining methods includefusing (e.g. heat fusion), welding (e.g. ultrasonic welding) and joiningby adhesive methods (e.g., gluing). Combinations of these materials andmethods are contemplated by this invention. In one embodiment, forexample, the distal end of the middle tube 4 is joined to the proximalend of the sleeve tip 16 by a middle connection ring 21 that providesadhesion, as exemplified in FIGS. 1A, 2, and 3.

In one embodiment, a proximal ring sealingly connects the retractablesleeve structure to the inner tube within the housing. The proximal endof the retractable sleeve structure may further comprise a handledesigned to facilitate moving the retractable sleeve structure from adistal position within the housing structure to a proximal position. Theretractable sleeve structure further comprises a sealable port. Theretractable sleeve structure together with the inner tube form a sealedchamber, in which fluid may be added or removed through the sealableport. For the purpose of this application, “fluid” is understoodaccording to its proper definition in the area of physics, inclusive ofany substance that moves when exposed to shearing forces. “Fluid”therefore includes without limitation, substances in a gaseous phase aswell as substances in a partial or wholly liquid phase, such as water,water-based solutions, saline, oils or gels. The retractable sleevestructure may be retracted by sliding the handle from a first distalposition to a second more proximal position, thereby withdrawing andunfolding the sleeve tip and releasing the device. Because the outertube and the inner tube are fixedly connected to the housing structure,the outer and inner tubes are not affected by sliding the handle of theretractable sleeve structure.

The invention also relates to a method of deploying an intravasculardevice. The first deployment step comprises pressurizing the retractablesleeve structure with fluid. In one embodiment, the retractable sleevestructure is packaged at neutral air pressure such that the operatorwill pressurize the retractable sleeve structure with fluid prior to itsuse. During pressurization of the retractable sleeve structure withfluid, it may be necessary to remove remaining air from the sleeve. Incertain embodiments, a micro-orifice in the sleeve tip allows remainingair to evacuate the sealed chamber prior to or while the sealed chamberis filled with a pressurized fluid by applying a pressure of 1-10 atmthrough the sealable port. The micro-orifice preferably has a diameterin the range of 30-40 micrometers, thus allowing air to exit the sealedchamber while generally minimizing the pressurized fluid flow throughthe micro-orifice. Insertion and pressurization of the fluid can beachieved using methods that are well known in the art. In oneembodiment, physiologically-compatible fluid is used in the sealedchamber, such as, for example, a physiologically-compatible salinesolution. Other biocompatible fluids may similarly be used as is knownin the art. The sealed chamber may be filled to a pressure in the rangeof 1-10 Atm. In one preferred embodiment, the sealed chamber ispressurized to 4 Atm.

Employment of a pressurized fluid may provide an advantage bymaintaining the adjacent inner and outer portions of the fold of thesleeve tip apart from each other by at least a few micrometers so as toavoid rubbing. The method of evacuating air through a micro-orifice inthe distal portion of the sleeve tip may be advantageous compared toother methods known in the art for evacuating air (e.g. by applicationof a vacuum) because the micro-orifice enables evacuation of a greaterpercentage of residual air from the sealed chamber.

In one embodiment, use of a fluid may comprise a hydrogel or othermaterial with similar properties, including water absorbency andhydrophilic properties. In this embodiment, hydrogel is applied duringthe manufacturing stage, for example, by coating the inner surface ofthe sleeve tip. Hydrogel may also be introduced through the sealableport following the manufacturing stage. Upon contact with an aqueousliquid, hydrogel increases in volume, thus assisting in evacuating airthrough the micro-orifice, while simultaneously increasing the axialrigidity of the sleeve tip. The method of applying hydrogel to thesealed chamber is thus advantageous in evacuating air and providing thedesired level of axial rigidity upon introduction of an aqueous liquidwithout the need to pressurize the fluid within the sealed chamber as aseparate step.

The method of deploying an intravascular device further comprisesnavigating the sleeve tip to the target site in the body lumen so thatthe mounted device is positioned at the target site for deployment. Thesleeve tip is delivered to the target site in the body lumen by methodsknown in the art. The employment of thin, flexible, light-weightmaterials, as well as the use of pressurized fluid—and/or a hydrogel—inthe retractable sleeve structure, enables the navigation of the cathetersystem via tortuous lumen while minimizing axial and frictional forcesapplied on the catheter.

Referring now to the drawings wherein the figures are for purposes ofillustrating preferred embodiments of the present invention only, andnot for purposes of limiting the scope of the invention in any way, FIG.1A shows one embodiment of the catheter system 20 in a pre-deploymentstate having a proximal end and a distal end. The catheter systemincludes a guide wire 9 comprising a distal end 13 extending into thelumen during deployment and a proximal end 14 that remains outside thebody during deployment. The guide wire 9 extends through the lumen ofinner tube 5. The inner tube 5 has a proximal end and a distal end. Theinner tube 5 extends through housing structure 8 having a distal end 8 aand a proximal end 8 b. In this embodiment, the housing structure 8 hasa length equal to or greater than a distance 2L, i.e. a length twicedistance L (detailed herein below). The housing structure 8 includes adistal opening 31 and a proximal opening 32. The inner tube 5 extendsthrough distal opening 31 of the housing structure 8 to the proximalopening 32, to which the inner tube 5 is affixed. In FIG. 1A, the innertube 5 traverses the proximal opening 32 through the housing structure8. Outer tube 3 forms a lumen through which extends the inner tube 5 andguide wire 9. The outer tube 3 is affixed to the housing structure 8 atdistal opening 31.

The outer tube 3 and the inner tube 5 are affixed to the housingstructure 8, and form a consistent radial space between the outersurface of the inner tube 5 and the internal surface of the outer tube3. A retractable sleeve structure 2 extends through the radial spaceformed by outer tube 3 and inner tube 5. The retractable sleevestructure 2 comprises middle tube 4 having a proximal end and a distalend and a sleeve tip 16 having a proximal end and a distal end. Thesleeve tip 16 may have a micro-orifice 18 to permit air to evacuate thesealed chamber 15 prior to or while the sealed chamber 15 is filled witha pressurized fluid 10 through the sealable port 11. In one embodiment,as shown in FIG. 1A, the proximal end of middle tube 4 is sealinglyconnected to the inner tube 5 via proximal ring 7. In the embodiment ofFIG. 1A, the proximal ring 7 forms a fluid-tight, moveable seal againstinner tube 5. The retractable sleeve structure 2 further comprises ahandle 6 which may be utilized to control movement of the retractablesleeve structure 2, including movement of the slideable proximal ring 7along inner tube 5. As shown in FIG. 1A, the sealable port 11 is locatedin the handle 6; the sealable port 11 may be used to control thecontents and pressure of fluids in the sealed chamber 15 formed by theretractable sleeve structure 2 together with the inner tube 5. Inanother embodiment, the sealable port 11 may be positioned on the middletube 4 separate from the handle 6. The distal end of middle tube 4 isfixed to the proximal end of the sleeve tip 16. The distal end of thesleeve tip 16 may be sealed to the inner tube 5 via a distal ring 12 asshown in FIG. 1A. Pressurized fluid 10 is introduced into the sealedchamber 15 formed by the retractable sleeve structure 2 and inner tube 5through the sealable port 11. Similarly, the pressure of the fluid inthe retractable sleeve structure may be controlled via the sealable port11. Generally, the housing structure of any embodiment described hereinmay be an open or closed structure.

In one embodiment, the retractable sleeve structure has, whilepressurized, a substantially constant outer diameter along thelongitudinal extent of the middle tube 4 and sleeve tip 16. The sleevetip 16 radially extends a radial distance W from inner tube 5 and foldsonto itself forming a sheath around the crimped device 1. While thedevice may be any transluminally implantable intravascular device, thedevice 1 depicted in FIG. 1A and other Figures is a cylindrical stent,here illustrated in a crimped state. Fold 17 of the retractable sleevestructure 2 extends a longitudinal distance L which is equal to orgreater than the length of the intravascular device. In other words, thelength of the material making up the fold is equal to or greater thantwice the length of the mounted intravascular device.

FIG. 1B shows an enlarged portion of the catheter system 20, includingthe fold 17 of the sleeve tip 16 that forms a radial distance W betweenthe retractable sleeve structure 2 and the inner tube 5. The spaceformed between the sleeve tip 16 and inner tube 5 is suitable formounting a device 1 prior to deployment. In this embodiment the foldlength L (shown in FIG. 1A) closely matches the length of the mounteddevice 1.

In one embodiment, the method of deploying an intravascular devicefurther comprises retracting the retractable sleeve structure 2, wherebythe sleeve tip 16 is withdrawn or peeled away from the device in aproximal direction, thereby releasing the device 1. FIG. 1A and FIGS. 2through 4 illustrate the steps according to one embodiment of theinvention. With reference to FIG. 1A, the handle 6 of the retractablesleeve structure 2 begins in a first position near the distal end of thehousing structure 8. In one embodiment of this invention, the retractionstep comprises applying a proximally-directed force on the handle 6,thereby sliding the proximal ring 7 in a longitudinal direction alongthe inner tube 5. As shown in FIG. 2, as the proximal ring 7 slides adistance of approximately one-third of 2L, and the sleeve tip 16withdraws a longitudinal distance of approximately one-third of L.Because the outer tube 3 and inner tube 5 are fixedly connected to thehousing structure 8—which remains stationary during this step—only theretractable sleeve structure is affected by applying aproximally-directed force to the handle 6 and sliding the handle 6 in aproximal direction. This step is further illustrated by FIG. 3, whereinthe handle 6 and proximal ring 7 slides a distance of approximatelytwo-thirds of 2L, and the sleeve tip 16 therefore withdraws alongitudinal distance of approximately two-thirds of L. The step iscompleted, as shown in FIG. 4 with the full deployment of the device 1by sliding the proximal ring 7 and handle 6 the entire distance 2L to asecond position adjacent to the proximal end 8 b of the housingstructure 8, thereby withdrawing the sleeve tip 16 a distance L. Theretraction of the retractable sleeve structure 2 thereby releases thedevice 1 while minimizing friction on the exterior surface of the device1. The device 1 is then able to expand into the target site of the bodylumen. Throughout the process, the proximal ring 7 maintains afluid-tight seal against inner tube 5, thus maintaining pressurizationof the retractable sleeve structure 2.

FIG. 4 shows the catheter system 20 in a post-deployment state. Theretraction of the retractable sleeve structure 2 released the device 1within the body lumen. As the retractable sleeve structure 2 isretracted, the sleeve tip 16 is peeled away from the intravasculardevice thereby releasing it into the body lumen. Retraction of thesleeve structure a distance of 2L will result in withdrawal of thesleeve tip 16 a length L, thus eliminating the fold.

FIG. 5A shows another embodiment of the catheter system 20, wherein theretractable sleeve structure 2 further comprises a collapsible proximalportion sleeve 24 sealingly attached at its proximal end to the proximalend 8 b of the housing structure 8, and sealingly attached at its distalend to the middle tube 4. The collapsible proximal portion sleeve 24 ismanufactured of a highly flexible material, such as, for exampleultra-thin polyethylene terephthalate (PET) or a Polyimide (PI). In thisembodiment, the proximal end of the retractable sleeve structure 2 isintegral with the proximal portion of the housing structure 8, andfurther includes a spout 28 which comprises a sealable port 29. Bycontrast with the handle comprising a sealable port of the previousembodiment, the spout 28 does not move during the deployment process.Rather, as shown in FIG. 5A, the retractable sleeve structure 2 includesa handle 23 which in this embodiment is formed as a knob positioned atthe distal portion within the housing structure 8. During deployment, aradial force is applied to the handle 23, thereby axially compressingthe retractable sleeve structure 2; simultaneously, a force in theproximal direction is applied to the handle 23, thereby collapsing theproximal portion sleeve 24, for example, into accordion-like folds asshown in FIG. 5B. In order to collect and collapse in an accordion-likemanner a distance of 2L, the knob may be moved back and forth severaltimes as shown by the two sided arrow. As the proximal portion sleeve 24collapses, the sleeve tip 16 therefore withdraws. The sleeve tip 16 mayhave a micro-orifice 18 as shown in FIG. 5A to permit air to evacuatethe sealed chamber 15 during this process, or prior to or while thesealed chamber 15 is filled with a pressurized fluid 10 through thesealable port 29. In other embodiments, the proximal portion sleeve 24may collapse in other manners as known in the art. Because theembodiment illustrated in FIGS. 5A and 5B is based on collapsibleproximal portion sleeve 24, this embodiment has the advantage of notrequiring housing structures equal to or longer than twice the length ofthe stent (i.e. the length of the housing can be shorter than 2L),thereby making the catheter system more compact and easier to use.

The method of deploying the intravascular device of FIGS. 5A and 5B isaccomplished by retracting the retractable sleeve structure 2 through aseries of steps involving a handle 23, as shown in FIGS. 5A and 5B. Theretraction begins, as shown in FIG. 5A, with the handle 23 in a firstposition near the distal end 8 a of the housing structure 8 along thecollapsible proximal portion sleeve 24 of the retractable sleevestructure 2. The first step comprises applying a compression force tothe handle 23, thereby gripping the handle 23 against the proximalportion sleeve 24. As illustrated by FIG. 5B, the next step comprisespulling the handle 23 in a proximal direction while maintaining acompression force, thereby collapsing the collapsible proximal portionsleeve 24 toward the proximal end 8 b of the housing structure 8 andreleasing the intravascular device. In one embodiment, the collapsibleproximal portion sleeve 24 folds in an accordion-like manner, as shownin FIG. 5B. The method further comprises reducing the compression forceon the handle 23 and returning the handle 23 to the first position nearthe distal end 8 a of the housing structure 8. These steps are repeateduntil the collapsible proximal portion sleeve 24 of the retractablesleeve structure 2 has fully collapsed, thereby withdrawing the sleevetip 16 and releasing the device 1, viewed either through an imagingmedium (e.g. angiography) or as indicated by an abrupt increase inresistance to the retraction force on the handle 23. In anotherembodiment of the invention, employment of a wheel in this step may beused to apply a force to the proximal portion sleeve 24 in the proximaldirection.

FIG. 6A shows another embodiment of the catheter system 20, wherein theretractable sleeve structure further comprises a rear retractableportion 25. The rear retractable portion 25 has a distal end 26 that isjoined to the proximal end of the middle tube 4, and is sealinglyattached at its proximal end to an insertion tube 27. The rearretractable portion 25 may be manufactured from flexible materials, forexample, polyethylene terephthalate (PET), Polyimide (PI), Nylon 12 orsuitable materials readily understood in the art. The insertion tube 27surrounds the inner tube 5 with a lumen between the insertion tube 27and inner tube 5 to enable fluid or air to pass from the insertion tube27 to the sealed chamber 15 at the distal end of the insertion tube 27.At the proximal end of the insertion tube 27, the insertion tube 27connects to a spout 28 affixed to the inner tube 5. The spout 28 furthercomprises a sealable port 29 for controlling the contents and pressureof the fluids in the sealed chamber 15. In another embodiment, thesealable port 28 may be positioned on the rear retractable portion 25separate from the spout 29. As shown in FIG. 6A, the sleeve tip 16 mayhave a micro-orifice 18 to permit air to evacuate the sealed chamber 15prior to or while the sealed chamber 15 is filled with a pressurizedfluid 10 through the sealable port 29. The insertion tube 27 may bemanufactured from a metal or a biocompatible polymer. During deployment,a force is applied in the proximal direction at the proximal end of therear retractable portion 25. Thus, the rear retractable portion 25 foldsonto itself and over the insertion tube 27 in the proximal direction, asshown in FIG. 6B. During this process, the sleeve tip 16 thereforewithdraws. Because the embodiment illustrated in FIGS. 6A and 6B isbased on rear retractable portion 25, this embodiment has the advantageof not requiring housing structures equal to or longer than twice thelength of the stent (i.e. the length of the housing can be shorter than2L), thereby making the catheter system more compact and easier to use.

The method of deploying the intravascular device of FIGS. 6A and 6B isaccomplished by retracting the rear retractable portion 25 through oneof several possible means. In one embodiment, the housing structure 8includes a wheel 35 having an edge 36 that contacts the exterior surface37 of the rear retractable portion 25, as shown in FIG. 6C. Uponrotation of the wheel 35, frictional force of the edge 36 against theexterior surface 37 results in the rear retractable portion 25 foldingonto itself and over the insertion tube 27. Other mechanical meansreadily known to one skilled in the art may be employed to apply aproximal force to the rear retractable portion 25.

FIG. 7A shows a cross-sectional view of another embodiment of thecatheter system 20, wherein the retractable sleeve structure 2 furthercomprises a curved inner tube portion 30 that is connected to theproximal end of inner tube 5 and extends in a curved direction withinthe housing structure 8. The curved inner tube portion 30 ismanufactured from a metal or a biocompatible polymer and may coil up toand beyond 360 degrees within the housing structure 8. The middle tube 4(having a proximal end 46), handle 6 and proximal ring 7 follow thecurved inner tube portion 30. Handle 6 further comprises a sealable port11 for controlling the contents and pressure of fluids in the sealedchamber 15. In another embodiment, the sealable port 11 may bepositioned on the middle tube 4 separate from the handle 6. In thisembodiment, the housing structure has a first end 33 that is affixed toouter tube 3 and a second end 34 that is affixed to the curved innertube portion 30. During deployment, a force in the proximal direction isapplied to the handle 6, thereby retracting the handle 6 and theretractable sleeve structure 2 over the curved inner tube portion 30 asshown in FIG. 7B. During this process, the sleeve tip 16 thereforewithdraws. The sleeve tip 16 may have a micro-orifice 18 to permit airto evacuate the sealed chamber 15 prior to or while the sealed chamber15 is filled with a pressurized fluid 10 through the sealable port 11.Because the embodiment illustrated in FIGS. 7A and 7B is based on curvedinner tube portion 30, this embodiment has the advantage of notrequiring housing structures equal to or longer than twice the length ofthe stent (i.e. the length of the housing can be shorter than 2L),thereby making the catheter system more compact and easier to use.

Many different methods may be employed to mount the intravascular deviceonto the inner tube of the catheter system prior to deployment. Onemethod is illustrated by FIGS. 8A-8D. The first step of one embodimentis shown in FIG. 8A and comprises compressing at least a portion ofintravascular device 1, for example a fully crimped stent, around aninner tube 5 using a holding device 19. The next step, shown in FIG. 8B.comprises applying a force in the distal direction, for example to thehandle of the sleeve tip (not shown), such that the retractable sleevestructure moves in the distal direction to incrementally extendlongitudinally over an exposed residual portion of the intravasculardevice. The axial rigidity of the sleeve tip 16 is accomplished by fluidpressurization through means discussed above. The method furthercomprises releasing the holding device 19 and pulling the cathetersystem proximally, as shown in FIG. 8C. In the next step, the processrepeats, as shown in FIG. 8D. The holding device 19 is compressedagainst a more distal location on the device 1 than in the previous stepand at each cycle the fold of the sleeve tip is extended incrementallyin the distal direction to eventually cover or sheath the entire device.In one embodiment, the retractable sleeve structure 2 may be assembledwith pressurized fluid in the sealed chamber 15. The sealed chamber maybe deflated once the device is mounted and prior to use.

In another embodiment of the intravascular device mounting method, themethod comprises placing a intravascular device in a crimped state onthe inner tube while the handle of the retractable sleeve structure ispositioned near the proximal end of the housing structure, such that thesleeve tip is fully withdrawn. In the next step of this embodiment, aforce in the distal direction is applied to the handle, such that theretractable sleeve structure moves distally against the mountedintravascular device. Upon contact with the mounted intravasculardevice, the sleeve tip naturally folds around the intravascular device.A holding device is positioned at the distal end of the intravasculardevice holding it in place as the sleeve tip folds over the device. Thefold of the sleeve tip is extended to cover or sheath the entireintravascular device.

The device may be any stent or graft device, which are well known in theart. Any stent design may be utilized in connection with the presentinvention. In one example, the stent consists of separate segmentsdesigned to expand independently from each other as the sleeve tip iswithdrawn; however, it should be understood that the invention is notlimited to any particular stent design or structure. A stent or grafthaving either separate segments or a unitary design (i.e., withoutseparate stent segments designed to expand independently from eachother) may be used with this invention, as well as stents that expand atdifferent rates along the longitudinal axis of the stent. The inventionfurther contemplates stents or grafts having diameters of variable sizesand different lengths. One non-limiting example design is the NIRflexstent which is manufactured by Medinol, Ltd., as described in U.S. Pat.No. 6,723,119, which is incorporated herein in toto, by reference.Another example of a suitable self-expanding stent is described in U.S.Pat. Nos. 6,503,270 and 6,355,059, for example, which are alsoincorporated herein in toto, by reference.

It will be appreciated by persons having ordinary skill in the art thatmany variations, additions, modifications, and other applications may bemade to what has been particularly shown and described herein by way ofembodiments, without departing from the spirit or scope of theinvention. Therefore it is intended that scope of the invention, asdefined by the claims below, includes all foreseeable variations,additions, modifications or applications.

The invention claimed is:
 1. A catheter system for delivery anddeployment of an intravascular device, the catheter system having adistal end and a proximal end, comprising: an inner tube having a firstlumen; an outer tube having a second lumen, wherein said inner tubeextends through said second lumen; a retractable sleeve structurepositioned between the inner tube and outer tube, said retractablesleeve structure comprising a middle tube and a sleeve tip, the middletube having a proximal end and a distal end, the middle tube coaxiallyextending substantially along the length of the inner and outer tubes,and the sleeve tip having a distal end sealed to the inner tube and aproximal end fixed to the distal end of the middle tube, wherein in apre-deployment state, the sleeve tip forms a fold over the intravasculardevice to form a double layered sheath; and a housing structure at theproximal end of said catheter system, said housing structure having adistal end and a proximal end, wherein the inner tube is fixedlyconnected to the housing structure, the retractable sleeve and the innertube form a sealed chamber, and in the pre-deployment state, theintravascular device is mounted in a radial space between the inner tubeand the sleeve tip in the double-layered sheath configuration.
 2. Thecatheter system of claim 1, said sleeve tip having a first configurationwherein the intravascular device is fully enveloped by said sleeve tipin said first configuration and a second configuration after deploymentof said intravascular device.
 3. The catheter system of claim 1, whereinthe outer tube and inner tube are affixed relative to each other.
 4. Thecatheter system of claim 1, wherein said retractable sleeve structurecomprises a sealable port.
 5. The catheter system of claim 4, whereinthe sealable port is located in a handle.
 6. The catheter system ofclaim 1, wherein the sleeve tip includes a micro-orifice having adiameter of 30-40 micrometers.
 7. The catheter system of claim 1,wherein the sleeve tip comprises ultra-thin polyethylene terephthalate.8. The catheter system of claim 1, wherein the sleeve tip comprisespolyimide.
 9. The catheter system of claim 1, further comprising adistal ring connecting the sleeve tip to the inner tube.
 10. Thecatheter system of claim 1, further comprising a handle connected to theretractable sleeve at the proximal end of the middle tube.
 11. Thecatheter system of claim 10, wherein the handle further comprises aproximal ring connecting the middle tube to the inner tube.
 12. Thecatheter system of claim 1, wherein the sealed chamber contains a fluid.13. The catheter system of claim 1, wherein the sealed chamber containsa hydrogel.
 14. The catheter system of claim 1, wherein the sleeve tipis movable relative to the inner and outer tubes.
 15. The cathetersystem of claim 1, further comprising a guidewire.
 16. The cathetersystem of claim 1, wherein said inner tube is immovably affixed to thehousing.